New Zealand's advertising regulator has clashed with academics over a study that concluded advertising rules are ineffective in protecting children from exposure to unhealthy food marketing on television.

In a study published in the journal Public Health Nutrition​ in May, researchers randomly selected four weekdays and four weekend days to record 432 hours of footage from three free-to-air-channels, with audience ratings used to identify children's peak viewing times.

They found that the majority of foods advertised (n=1807) were 'unhealthy', with 68·5% of the ads including at least one food not permitted to be marketed to children, according to the World Health Organization (WHO) nutrient profiling model.

"One-third of unhealthy food advertisements included a promotional character and one-third a premium offer. About 88% of unhealthy food advertisements were shown during children's peak viewing times," ​they wrote.

"If the WHO (model), instead of the current nutrient profiling model, was used to restrict unhealthy food advertising to children, the average impact would be reduced by 24% during weekdays and 29% during weekend days."​

Lack of distinction?

In response to the findings, Advertising Standards Agency (ASA) CEO Hilary Souter said there were "several limitations to the research".​

She wrote a letter to the editor​ of the journal stating there was a lack of a distinction between adverts meant for children and adults, and questioned the "assumption"​ that the use of a discount implied children were being targeted.

Souter was also unhappy that food adverts were deemed unhealthy if just one product on display failed to meet the WHO nutrient profile, and said the study had failed to take into account the "restrictive advertising environment"​ during peak children's viewing hours, versus those when parental supervision would be present.

She ended by drawing attention to the new Children and Young People's advertising code, which has now been fully implemented.

"It introduces a clear restriction on targeting children under 14 years with occasional food and beverage advertising. ​The ASA has run briefings to ensure (the) industry is aware of the requirements of the new code, and there has been a high level of engagement."​

Adult impact

The academics, Stefanie Vandevijvere, Alanna Soupen and Boyd Swinburn, acknowledged in a response​ that the new code was "a small step"​ in the right direction, but said it had severe shortcomings.

Most noticeable, they claimed, was the ASA ruling that an advert could be deemed to be targeting children if they comprise 25% or more of the total audience.

They said the rule should apply to when a set percentage of children are watching TV, because "it does not make sense to include adults in the denominator"​.

Addressing Souter's concerns about branding an advert unhealthy if only one product on display failed to meet the WHO nutrient profile, they argued it was a "legitimate methodical choice"​, but acknowledged there was "no gold standard"​ for dealing with this issue, saying the ASA itself hadn't specified in the new code how to tackle the problem.

They added that the other limitations specified by Souter were incorrect, as it was impossible and irrelevant in such a study to account for whether parents were present when their children were watching TV.

"There is no evidence to show that the impact of unhealthy food advertisements is less when children are unsupervised than when they are not. ​It makes most sense to protect children by simply not airing unhealthy food advertisements specifically targeted at them."​